A woman is recently widowed, the days of Iddah are not over yet, her son's wedding is approaching so she wants to attend the Nikaah ceremony, as the father is not there so she has to be there, some Mufti has said that she can not see the face of the groom till Iddah, etc., as per my information the night stay without Mahram is prohibited for a widow till Iddah, also there is no concept of death ceremonies to be prolonged and binding a woman to sit in the house and not to go out for necessary shopping, etc, so in this regard please inform me about the right thing.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

A woman whose husband is dead is obliged to mourn her husband during her waiting period, as the Prophet said: "It is not permissible for a woman who believes in Allaah and the Last Day to mourn any dead person more than three days, except her husband, she should mourn him four months and ten days." [Al-Bukhari and Muslim] We have already issued Fatwa 88684 clarifying the 'Iddah (the waiting period) for a woman whose husband died and what she should or should not do during this period, so please refer to it. 

As regards saying that she is not allowed to see the face of the groom, there is no evidence on this. However, she should not wear elaborate garments, or apply perfume, or beautify herself, or do anything that attracts other people to look at her. As regards her looking to a woman who beautified herself [either by the latter putting make up or jewelry and other adornments] then this is not among the prohibitions that she is not allowed to do while mourning her dead husband.

With regard to her looking at the bridegroom if he is a Mahram (a non-marriageable relative) then there is no harm in this, but if he is not, then a woman is obliged to lower her gaze whether or not she is during her waiting period.

As regards a woman who is still in her waiting period and wants to go to a marriage ceremony, then the jurists stated that a woman, who is divorced an irrevocable divorce or whose husband died, is permitted to go out to attend a marriage ceremony but she should not beautify herself and she should spend the night in her own home only. Therefore, according to this view, the mother is permitted to attend her sons' marriage ceremony without beautifying herself and she is obliged to spend the night in her own home. 

Allaah Knows best.